1. Field of the Invention
The present application relates to a manufacturing method of a semiconductor device and the semiconductor device.
2. Description of the Related Art
For multilevel metalization of semiconductor integrated circuit (LSI), a copper (Cu) film which has a low specific electrical resistance is used, and a Damascene interconnection method, which buries Cu films into grooves and via holes formed in interlayer dielectric films, has been mainly used. A width of interconnection line becomes smaller with the miniaturization of LSI and a thickness of the line has a tendency to be thinner for decreasing the capacity between lines. For this reason, in the fine Damascene interconnection, an area ratio of a barrier metal layer having a high specific resistance in a line cross sectional area has a large effect on the line resistance. That is, as a thickness of the barrier layer is thinner, the resistance of the Damascene interconnection becomes lower. However, it is simultaneously required for the barrier metal layer to prevent the diffusion of Cu atoms to the interlayer dielectric films, to have an adhesiveness with the Cu film, and to have an adhesiveness with the interlayer dielectric film.
Particularly, the adhesiveness between the barrier metal layer and the Cu film is very important for the resistance to an electro-migration (EM) of the wirings and a stress-migration (SM) of the wirings. Further, the barrier metal layer is required to have the most thin film thickness to satisfy above requirements and to be formed so as to conform to the shape of bottom surface and side surface of the groove formed in the layer insulation film with a uniform thickness.
Next, we will describe the recent state with respect to the forming of a thin barrier metal layer. In a general physical vapor deposition method (PVD method), it is difficult to cover the difference in level. Therefore, in a dual Damascene structure which is formed by burying grooves and via holes formed in an interconnection dielectric film with metals, it is difficult to form conformal barrier metal layers by using the PVD method. For that reason, an ionization PVD method has been developed to use for forming the barrier metal layer, the method including biasing a substrate, drawing metal ions thereto to improve bottom coverage, and using re-sputtering effect of metal or forming-gas ions to improve side coverage.
However, accompanying with further requirements of miniaturization and high aspect ratio of interconnection lines, conformal forming of barrier metal layer will be more and more difficult hereafter. On the other hand, although it is possible to form conformal barrier metal layers using the chemical vapor deposition method (CVD method), it is impossible to adapt a high temperature process at the interconnecting process, due to the problem of poor SM property. For that reason, in the CVD method, there is a problem that feed gases for forming the barrier metal layer which can be decomposed at an allowable temperature of interconnecting processes are limited.
Further, as a conformal film forming method of a very thin film, the atomic layer depositing method (ALD method) which stacks one atomic layer at a time on a surface of the substrate layer. The ALD method is not suitable for forming a thick film, but it is possible to form a very thin film and to cover the difference in level by the method. However, also even in the ALD method, there is a problem as the CVD method that it is difficult to thermally decompose feed gases within an allowable temperature range at the interconnecting processes.
On the other hand, in a recent interlayer dielectric film, in order to suppress a signal delay an insulation film having a low dielectric constant has been used. In the low dielectric constant insulation films, in both organic type insulation films and inorganic insulation films, much carbon (C) and much pores are contained and oxidation sources such as water (H2O) are trapped. An adhesiveness of the barrier metal layer with the Cu film is determined by two kind of adhesiveness. The first is an adhesiveness determined according to material, and the second is an adhesiveness with a deterioration of the barrier metal layer which generates with passage of time. Particularly, the change of adhesiveness with passage of time is very serious, because the changes occur not only in the manufacturing processes but also in an actual use. The changes in an actual use cause SM and EM errors and the like. In the processes of work including plasma irradiation, electron beam irradiation or ultraviolet irradiation and in a curing process of an insulation film, molecules containing carbons are emitted, the insulation films are damaged, and water is easily adsorbed at sites of which emitted carbons are bonded.
One of the reasons of deterioration of barrier metal layer with passage of time during the manufacturing processes or actual uses is based on the oxidation of barrier metal layers with oxidation sources containing in the insulation film and the degradation of adhesiveness with Cu. And in other case, the barrier metal layers are carbonized with molecules containing carbon (C) to be deteriorated.
As mentioned above, it is considered that to suppress the deterioration of barrier metal layers and to secure the adhesiveness will be more and more difficult hereafter. Further although JP-A 2000-269213, for example, has disclosed a process of forming oxidation film at boundary surface in advance, the process could not obtain desired results, because oxides having large valence and low density are formed when the oxides are actively formed.